My choice would be Uncanny as of right now. I am loving what Matt Fraction is doing with the X-men as a whole. I would say if you want to know whats going on with the x-men as a whole you should be reading Uncanny because Fraction is doing a great job of using every member of the x-men from time to time rather then just a select team if x-men who go on adventures. If you want to read about a select group of X-men on a team then i would read Legacy (if you like Rouge and the students) or New Mutants (if you like the original group of students who are now grown up and on a team of their own)